<!doctype html>
<!--
Copyright 2020 The Immersive Web Community Group

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-->
<html>

<head>
  <meta charset='utf-8'>
  <meta name='viewport' content='width=device-width, initial-scale=1, user-scalable=no'>
  <meta name='mobile-web-app-capable' content='yes'>
  <meta name='apple-mobile-web-app-capable' content='yes'>
  <link rel='icon' type='image/png' sizes='32x32' href='../favicon-32x32.png'>
  <link rel='icon' type='image/png' sizes='96x96' href='../favicon-96x96.png'>
  <link rel='stylesheet' href='../css/common.css'>

  <title>Quad Layer</title>
  <!-- Stereo layer dependency -->
  <script src="../js/wglu/wglu-program.js"></script>
  <script src="../js/wglu/wglu-url.js"></script>
  <script src="../js/stereo-util.js"></script>
</head>

<body>
  <header style="max-width: 800px;">
    <details open>
      <summary>Quad Layer</summary>
      <p>
        This sample shows how to draw a scene into a quad layer.
        Quad layers can be used for implementing small panels that
        can be placed in front of the user containing text/image/video
        information. Its use cases are similar to those of a cylinder
        layer, but are generally favored when the panel is smaller.
        <a class="back" href="./index.html">Back</a>
      </p>
      <p>
        Image by Eric Cheng
      </p>
      <input type="checkbox" id="cyldIsStereo">Stereo quad layer</input><br />
    </details>
  </header>
  <main style='text-align: center;'>
    <p>Click 'Enter VR' to see content</p>
  </main>
  <script type="module">
    import { WebXRButton } from '../js/util/webxr-button.js';
    import { Scene, WebXRView } from '../js/render/scenes/scene.js';
    import { Renderer, createWebGLContext } from '../js/render/core/renderer.js';
    import { QueryArgs } from '../js/util/query-args.js';

    const CYLD_TEXTURE_MONO_PATH = '../media/textures/rect-mono.png';
    const CYLD_TEXTURE_STEREO_PATH = '../media/textures/rect-stereo-top-down.png';

    // If requested, use the polyfill to provide support for mobile devices
    // and devices which only support WebVR.
    import WebXRPolyfill from '../js/third-party/webxr-polyfill/build/webxr-polyfill.module.js';
    if (QueryArgs.getBool('usePolyfill', true)) {
      let polyfill = new WebXRPolyfill();
    }

    // XR globals.
    let xrButton = null;
    let xrSession = null;
    let xrRefSpace = null;
    let xrGLFactory = null;
    let xrFramebuffer = null;
    let stereoUtil = null;

    // WebGL scene globals.
    let gl = null;
    let renderer = null;
    let scene = new Scene();

    // Layer globals
    let projLayer = null;
    let cyldLayer = null;
    let cyldImageElement = null;
    let cyldIsStereo = false;
    let cyldTextureWidth = 0;
    let cyldTextureHeight = 0;

    function initXR() {
      xrButton = new WebXRButton({
        onRequestSession: onRequestSession,
        onEndSession: onEndSession
      });
      document.querySelector('header').appendChild(xrButton.domElement);

      if (navigator.xr) {
        navigator.xr.isSessionSupported('immersive-vr').then((supported) => {
          xrButton.enabled = supported;
        });
      }
    }

    function onRequestSession() {
      if (!xrSession) {
        navigator.xr.requestSession('immersive-vr', {
          requiredFeatures: ['layers'],
        }).then(onSessionStarted);
      } else {
        onEndSession();
      }
    }

    function initGL() {
      if (gl) { return; }
      gl = createWebGLContext({ xrCompatible: true, webgl2: true, });
      document.body.appendChild(gl.canvas);
      gl.clearColor(0.0, 0, 0, 0.0);

      function onResize() {
        gl.canvas.width = gl.canvas.clientWidth * window.devicePixelRatio;
        gl.canvas.height = gl.canvas.clientHeight * window.devicePixelRatio;
      }
      window.addEventListener('resize', onResize);
      onResize();

      renderer = new Renderer(gl);
      scene.setRenderer(renderer);

      // Util for rendering stereo layers
      stereoUtil = new VRStereoUtil(gl);
    }

    function onSessionStarted(session) {
      xrSession = session;
      scene.inputRenderer.useProfileControllerMeshes(session);
      session.addEventListener('end', onSessionEnded);

      initGL();

      xrFramebuffer = gl.createFramebuffer();
      xrGLFactory = new XRWebGLBinding(session, gl);

      cyldIsStereo = document.getElementById("cyldIsStereo").checked;
      let cyldImagePath = cyldIsStereo ?
        CYLD_TEXTURE_STEREO_PATH :
        CYLD_TEXTURE_MONO_PATH;

      session.requestReferenceSpace('local').then((refSpace) => {
        xrRefSpace = refSpace;
        projLayer = xrGLFactory.createProjectionLayer({ space: refSpace, stencil: false });
        session.updateRenderState({ layers: [projLayer] });

        // Loading texture is async, create layer and update render state when done
        let imageElement = document.createElement('img');
        imageElement.src = cyldImagePath;
        imageElement.onload = function () {
          cyldTextureWidth = imageElement.width;
          cyldTextureHeight = imageElement.height;
          cyldImageElement = imageElement;
          cyldLayer = xrGLFactory.createQuadLayer({
            space: refSpace,
            viewPixelWidth: cyldTextureWidth,
            viewPixelHeight: cyldTextureHeight / (cyldIsStereo ? 2 : 1),
            layout: cyldIsStereo ? "stereo-top-bottom" : "mono",
          });
          cyldLayer.width = 2;
          cyldLayer.height = 1;
          let pos = { x: 0, y: 0, z: -2 };
          let orient = { x: 0, y: 0, z: 0, w: 1 };
          cyldLayer.transform = new XRRigidTransform(pos, orient);

          session.updateRenderState({ layers: [cyldLayer, projLayer] });
        }

        session.requestAnimationFrame(onXRFrame);
      });
    }

    function onEndSession() {
      xrSession.end();
    }

    function onSessionEnded(event) {
      if (event.session.isImmersive) {
        xrButton.setSession(null);
      }
      xrSession = null;
      gl = null;
    }

    function onXRFrame(time, frame) {
      let pose = frame.getViewerPose(xrRefSpace);
      xrSession.requestAnimationFrame(onXRFrame);

      if (cyldLayer && cyldLayer.needsRedraw) {
        let glayer = xrGLFactory.getSubImage(cyldLayer, frame);

        // TEXTURE_CUBE_MAP expects the Y to be flipped for the faces and it already
        // is flipped in our texture image.
        gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
        gl.bindTexture(gl.TEXTURE_2D, glayer.colorTexture);
        gl.texSubImage2D(gl.TEXTURE_2D, 0,
          0, 0,
          gl.RGBA, gl.UNSIGNED_BYTE, cyldImageElement);
        gl.bindTexture(gl.TEXTURE_2D, null);
      }

      if (pose) {
        gl.bindFramebuffer(gl.FRAMEBUFFER, xrFramebuffer);
        scene.updateInputSources(frame, xrRefSpace);

        let views = [];
        for (let view of pose.views) {
          let viewport = null;
          let glLayer = xrGLFactory.getViewSubImage(projLayer, view);
          glLayer.framebuffer = xrFramebuffer;
          viewport = glLayer.viewport;
          gl.bindFramebuffer(gl.FRAMEBUFFER, xrFramebuffer);
          gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, glLayer.colorTexture, 0);
          gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.DEPTH_ATTACHMENT, gl.TEXTURE_2D, glLayer.depthStencilTexture, 0);
          views.push(new WebXRView(view, glLayer, viewport));
        }
        scene.drawViewArray(views);
      }
      scene.endFrame();
    }

    initXR();
  </script>
</body>

</html>
